We will recruit 60 healthy postmenopausal women to undergo transilial bone biopsy after double tetracycline bone labeling, 30 in Omaha and 30 in Detroit. The volunteers will be between ages 45 and 75. An 8 mm. biopsy core will be taken from an area 2 cm. posterior and inferior to the right anterior superior iliac spine. The specimens will be fixed, dehydrated, defatted and embedded in methyl methacrylate without decalcification. This sections will be examined by both light microscopy and fluorescence microscopy. Quantitative histomorphometry will be performed and will include all the static and dynamic measures currently used by bone histomorphometrists. The data will serve as normal control values for this age and sex cohort, in whom bone histomorphometry is most commonly performed and will be made available in reduced or unreduced form to qualified investigators. Further, the microscopic sections or the embedded specimens will be made available to qualified investigators to obtain normal data by their own methods. The availability of normal data for U.S. women for the first time will increase our ability to study the pathogenesis of bone disease in postmenopausal women.